Thermal capsulotomy tool and system

ABSTRACT

A system and tool for performing a capsulotomy procedure. The system includes an air pressure unit, a capsulotomy and movement control unit providing electrical current and movement control, and a capsulotomy tool, and an extendable-retractable burning element coupled to the tool. A capsulotomy and movement control unit provides electrical current to the burning element and movement control for extending and retracting the burning element. When the burning element is in a flattened, retracted configuration, the tip of the tool can be inserted through a relatively small corneal incision. Then, the burning element is opened to a circular, extended configuration, allowing a capsulotomy by applying an electrical pulse to the burning element. Optionally, predefined points of weakness allow removal of the tool should breakage occur during surgery.

The present application is a Continuation-in-Part of U.S. patentapplication Ser. No. 11/913,317 filed Nov. 1, 2007 by the Applicant.

FIELD OF THE INVENTION

The present invention relates to the field of cataract surgery. Morespecifically, the present invention relates to a system and tool forperforming a capsulotomy procedure.

BACKGROUND OF THE INVENTION

To date, over one million cataract surgeries are performed annually inthe United States, in which the anterior lens capsule must be opened togain access to the lens nucleus and allow removal of degeneratedcortical material. It is necessary to create a relatively large circularopening in the lens capsule in order to enter the lens interior and towithdraw matter from inside. Formation of this opening is known as acapsulotomy. It is important that the opening has smooth edges and istear resistant so that the lens contents can be easily removed throughthe opening. The lens opening is usually on the order of 5-7 millimetersin diameter, though this may vary.

Currently, two techniques for anterior capsulotomy are widely used: the“can-opener” technique and capsulorrhexis. In can-opener capsulotomy, asmall incision in the sclera or peripheral cornea is performed, then acystotome, knife, or needle is inserted through the incision and smallconnecting tears are made in the anterior lens capsule in a circularpattern. After a complete circle has been made by connecting the tears,a circular piece of the anterior capsule is grasped with forceps andtorn away along the perforations. Unfortunately, when opening thecapsule with numerous small capsular tears, the small tags that remainbecome a focal area of least resistance and can lead to tears, whichextend radially and posteriorly to the posterior capsule. Thedetrimental result is a loss of structural stability of the capsule andan increased likelihood of vitreous entry into the anterior chamber.

Capsulorrhexis denotes a circular central opening in the anteriorcapsule. This continuous opening eliminates the residual tags commonwith the can-opener technique described above. In capsulorrhexis, acapsular incision is made with a cystotome, and this incision is coaxedto form a circular shape by pushing the leading edge of the freshlytearing capsule with the cystotome in a non-cutting fashion or bygrasping the leading edge with forceps. This procedure is challengingfor the surgeon to control. The tearing motion can lead to anundesirable tear toward the equator and the posterior capsule, and thesize of the opening is difficult to dictate. Capsulorrhexis requires asignificant amount of skill and experience and to consistently obtainsuccessful results.

Opening the anterior capsule via either of the described techniques ofanterior capsulotomy is a delicate procedure and is widely considered tobe one of the most difficult steps in cataract surgery. A poorlyperformed anterior capsulotomy significantly hinders the subsequentsurgical steps and increases the probability of operative complications.Complications resulting from a poor capsulotomy include zonular stresswith subsequent breakage of the posterior capsule, vitreous loss, andlarge capsular tags preventing efficient lens removal. A poorcapsulotomy also prevents placement of an intraocular lens in thecapsular bag due to ill-defined capsular structures. The operative timeis lengthened and patient discomfort can be increased, along with therisk of postoperative complications and decreased visual acuity results.

With either of the above-described techniques for anterior capsulotomy,the size or position of the capsular opening is often not ideal. Thelocation, size, and configuration of the incision have importantconsequences. For example, an overly small capsular opening can impairthe safe removal of the lens nucleus and cortex and prevent properintraocular lens insertion into the lens capsule. In addition, a smallor eccentric capsular opening places excessive stress on the lenscapsule during surgery, placing the eye at risk for zonular and capsularbreakage.

Certain devices have been proposed to overcome the problems associatedwith conventional anterior capsulotomy techniques. For example, U.S.Pat. No. 4,766,897 issued to Smirmaul, and U.S. Pat. Nos. 5,269,787 and5,873,883 issued to Cozean Jr. et al. each disclose instruments thatinclude circular cutting members for incising the anterior capsule.However, use of such devices in small incision cataract surgery islimited due to their size. Specifically, the anterior lens capsule ofthe eye is shielded by the cornea and sclera, such that a passage woundmust be cut in the corneal or scleral tissue before any surgicalapparatus can reach the anterior capsule. It is desirable to limit thewidth of the passage wound incised on the corneal tissue, preferably to1-3 millimeters. A small wound decreases the scope of the surgicalclosing procedures, promotes rapid healing, minimizes astigmatism,reduces potential infections, and offers rapid visual rehabilitation.Therefore, the instrumentation employed in cataract surgery should becapable of passing through a small wound. Prior art cutting memberscannot be passed through a small corneal incision of 1-3 mm.

Burning tools exist in which heat is concentrated at the tip, and thetip is made to contact and burn a surgical site. In use of such burningtools for cataract surgery, an incision is made in the cornea, and thetip of tool is inserted through the incision and brought into contactwith the capsule, where it is activated to sear through the capsule. Theuse of prior art burning tools is restricted by the small size of theincision, as previously mentioned, which hampers introduction of a largetip having a circular shape of the appropriate size of the desiredseared area.

International application PCT/IL05/000461 by the Applicants describes aburning ring present at an oblique angle on the end of a narrow-diametershaft. The burning ring can therefore be introduced through a smallincision, and the oblique angle grants a relatively large ellipticalburn, with the largest axis of the burn being larger than the diameterof the shaft.

U.S. Pat. No. 6,066,138 to Sheffer et al. describes a searing cauterythat is retractable from within a handle, so that the cautery can beextended to its final size after insertion through the corneal incision.The Sheffer patent suffers from the disadvantage that the burning ringdoes not close a complete circle, as apparent in FIG. 1 b, with the areanear the handle not being seared. Therefore, it is still necessary tograsp that remaining area with a forceps, and form a tear that isdifficult to control. Additionally, since the searing ring is formedfrom a single metal wire extending substantially into the depths of thehandle, when the wire is heated electrically, it is difficult toinsulate the tool and prevent heating in unwanted areas. Searing couldaccidentally occur in other portions of the eye adjacent to the lens,since the handle of the tool could heat, and since the tool needs to beinserted considerably into the eye.

Other burning tools exist which have a small diameter tip, which isinserted through the incision, and used to burn a series of holes in thecapsule, arranged in a ring, which is then grasped with forceps and torninto a circular opening. It is difficult to manipulate the burning toolto form a series of burns that are reliably ring-shaped and are presentat the desired location, and form a ring of the desired size. Also, incataract surgery, the procedure is usually complicated by the need formultiple instruments: a cutting tool, an air pressure inlet, a waterpressure inlet, and related surgical and electrical equipment.

My previous invention, described in International Publication No. WO06/109290, disclosed a surgical tool which provides both regulatedheating and airflow pressure directed to a surgical site. The tool iscapable of passing through a relatively small corneal incision and caneasily form a large diameter ring-shaped opening in the capsule.

The tool overcame the need for multiple instruments in cataractsurgeries as it provides both regulated heating and airflow pressuredirected to a surgical site. Furthermore, the tool is convenient tohandle, can be inserted through a small diameter (1-2.8 millimeters)incision in the cornea, and is capable of reliably creating a uniformcircular-shaped opening of approximately 4-7 millimeters in the lenscapsule.

The surgical tool described in WO 06/109290, overcomes major problemsassociated with prior art tools. However, the scenario in which the toolbreaks while in the eye, was not addressed in my previous patent, andsince the possibility of failure during surgery always exists, thedesign of the tool should be such that in case of breakage, it will bepossible to remove the tool immediately from the eye without damage tothe eye.

The present invention enlarges on the previous concept, describing adesign aspect allowing straightforward removal of the tool from the eyein case of breakage of the tool during surgery, without damage to theeye.

SUMMARY OF THE INVENTION

Accordingly, it is a principal object of the present invention toprovide a thermal system and tool for the performance of a capsulotomythat effects formation of an opening in the lens capsule through the useof a short pulse of electrical current. The heat generated from thecurrent instantaneously burns an opening of a predetermined size in thelens capsule.

Moreover, the system and tool of the present invention is adapted formaintaining a pressurized airflow to the surgical site so thatadditional airflow control devices are not required.

Additionally, the system and tool of the present invention has anexpandable-retractable burning element that enables approaching the lensthrough a small corneal incision (about 1.5 millimeters) while allowingfor a capsulotomy having a diameter, for example, of about 5-7millimeters.

In accordance with a preferred embodiment of the present invention,there is provided a system for performing a capsulotomy procedure,comprising a capsulotomy tool comprising a main housing having a distalend and an extendable-retractable burning element coupled to the distalend of the main housing and a capsulotomy and movement control unit. Thecapsulotomy tool is in connection with the capsulotomy and movementcontrol unit for providing electrical current and movement control tothe burning element such that when the burning element is extended andheated, an opening is burned on the lens capsule.

According to a preferred embodiment of the present invention, theburning element comprises first and second electrically-conductive bandshaving opposite ends that are connected between the end of the innertube and the tip of the outer tube.

In a preferred embodiment, the first and second bands each have a grooveupon them, with the groove representing a predefined point of weakness.In the undesirable scenario in which the electrical current isexcessively high, breakage will occur at these predefined points ofweakness. Should this occur while the tool is within the eye, thelocation of the grooves upon the bands is such as to nevertheless allowretraction of the broken bands into the sleeve prior to the removal ofthe tool from the eye. The tool can be immediately removed from the eyewithout damaging the eye. Preferably, a single groove is present on eachband, and each groove is situated near the end of its respective band,close to the tip of the outer tube. The broken bands thus remainconnected at the end of the inner tube, and can be retracted and removedfrom the eye.

According to preferred embodiments of the present invention, the systemalso comprises a handle for connecting between the tool and thecapsulotomy and control unit. The burning element for performance of thecapsulotomy is retracted from the capsulotomy tool portion beyond thehandle, and this tool portion is for disposable, one-time use.

According to further preferred embodiments of the present invention, thesystem also includes an air pressure unit and airflow means coupled tothe air pressure unit for directing pressurized air to the surgicalsite.

In accordance with another preferred embodiment of the presentinvention, there is provided a tool for performing a capsulotomy,comprising;

-   -   (a) a main housing having a proximal end and a distal end;    -   (b) an extendable-retractable burning element coupled to the        distal end of the main housing and adapted for being switched        between a retracted configuration and an extended configuration;    -   (c) an airflow channel extending through the main housing and        terminating proximal to the burning element;    -   (d) airflow means coupled to the airflow channel for supplying        pressurized airflow; and    -   (e) capsulotomy and movement control means coupled to the main        housing for providing electrical current to the burning element        and movement control for controlling extending and retracting of        the burning element;        wherein the burning element is insertable within the eye through        a small corneal incision when the burning element is in a        retracted configuration, and the burning element is adapted to        perform a capsulotomy of a predetermined size when it is in an        extended configuration, and when an electrical current is        applied thereto.

Other features and advantages of the present invention will become morereadily apparent and understood from the detailed description sectionthat follows.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the invention with regard to theembodiments thereof, reference is made to the accompanying drawings, inwhich like numerals designate corresponding elements or sectionsthroughout and in which:

FIG. 1 is a side view of a capsulotomy tool, according to a preferredembodiment of the present invention;

FIG. 2 is a cross-sectional side view of a capsulotomy tool, accordingto a preferred embodiment of the present invention;

FIG. 3 a is a partial cross-sectional side view of the embodiment,showing the burning element of the tool in a completely retractedconfiguration;

FIG. 3 b is a second partial cross-sectional side view, showing theburning element of the tool as it is being advanced from within thesleeve of the tool;

FIG. 4 is a perspective view of a capsulotomy tool, showing the burningelement in an extended configuration;

FIG. 5 is a partial view of a capsulotomy tool, showing an enlargementof the burning element in a partially opened configuration;

FIG. 6 is a partial view of a capsulotomy tool, showing the burningelement in a completely opened configuration;

FIG. 7 a is a schematic view of part of a system for the performance ofa capsulotomy, according to a preferred embodiment of the presentinvention; and

FIG. 7 b is a general schematic diagrammatic view of a system for theperformance of a capsulotomy, according to a preferred embodiment of thepresent invention.

FIGS. 8 a-b illustrate the procedure for creating a corneal incision asa first step in cataract surgery;

FIGS. 9 a-b illustrate delivery of airflow in a second step in cataractsurgery performed using the invention;

FIGS. 10 a-b illustrate extension of the burning element from within thesleeve, as a third step in cataract surgery performed using theinvention;

FIG. 11 illustrates the fully expanded circular burning element of theinvention positioned upon the lens, moments before searing of the lensfor completion of a capsulotomy;

FIG. 12 illustrates the final capsulotomy, and the burning elementclosed and folded for removal from the lens.

FIG. 13 illustrates the fully retracted tool being removed from the eye,and the final capsulotomy formed.

FIG. 14 illustrates the problematic scenario in which random breakage ofthe burning tool bands occurred while the tool was within the eye.

FIG. 15 further illustrates the problematic scenario of FIG. 14, showingthat the upper segments of the broken band cannot be retracted into thesleeve.

FIG. 16 is a partial view of a capsulotomy tool, showing the burningelement in an extended configuration, with each band having a groovedefining a predetermined point of weakness.

FIG. 17 illustrates the structure of the bands after breaking atpredetermined weakness points, while the tool is still in the eye.

FIG. 18 illustrates the fully retracted tool being removed from the eye.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention discloses a capsulotomy tool, which has aretractable cautery ring, also known as a burning element. The burningelement is initially hidden within a sleeve. After the tool is insertedpast the capsular incision, the burning element is progressivelyextended from within the sleeve by sliding outwards severalconcentrically arranged tubes with which the element is associated.Finally, the burning element is fully opened to expand into a completecircular or complete oval shaped cautery, which is then heated to searthe lens. The complete circular or oval-shaped searing thus eliminatesthe need for tearing by forceps, which is potentially dangerous anddifficult to perform.

In the invention, heating is limited to the burning element, so there isno danger of searing inappropriate areas of the eye. The retractablenature of the burning element allows it to be introduced through a smallcapsular incision, yet provides burning on the lens at a diameter largerthan that of the small capsular incision. The tool additionally providespressurized airflow through its hollow center, alleviating the need fora separate airflow tool.

FIGS. 1-6 show a preferred embodiment for a capsulotomy tool 10,constructed and operated in accordance with the principles of thepresent invention.

Referring to FIG. 1, capsulotomy tool 10 includes a main housing 12having a distal end 14 and a proximal end 16. Main housing 12 includes aconnector 40 at proximal end 16 for facilitating connection of mainhousing 12 to a handle which is operably connected to a capsulotomy andmovement control unit and to an air pressure unit for providingelectrical current and pressurized air, respectively, to capsulotomytool 10. This will be described further herein with respect to FIGS. 7a-b.

Capsulotomy tool 10 includes a sleeve 52 that extends from distal end 14of main housing 12. Initially, sleeve 52 is disposed over surgicalelements of capsulotomy tool 10, to be described further herein. Sleeve52 is formed from a non-conductive material, such as plastic or Teflon,and has smooth sides such that entry into the eye can be achieved withminimal friction. The end of sleeve 52 is tapered around the edges. Thisserves to ease of entry into the eye after an incision has been made.Sleeve 52 also provides a seal against the corneal incision after theeye has been entered.

Referring to FIG. 2 and best shown in FIGS. 3 a-b, capsulotomy tool 10includes an outer tube 18 having a distal end 44. End 44 comprises a tip46 and an outer tube extension 48 having a truncated circumference thatextends between the completely tubular region (region not having atruncated circumference) of outer tube 18 and tip 46. The region whereouter tube 18 changes from a completely tubular construction toextension 48 has a beveled edge 50, which provides extra structuralsupport for outer tube extension 48, so that extension 48 can be made asthin as possible. Beveled edge 50 may be beveled to any suitable angle,for providing maximal support to extension 48.

Capsulotomy tool 10 also includes an inner tube 20 that passes throughthe central axis of main housing 12, and that extends from distal end 14of main housing 12 and through outer tube 18. The hollow center of innertube 20 defines an air channel 24 (see FIG. 2) for directing pressurizedairflow to the surgical site. Air channel 24 is operably coupled to theair pressure unit (described below in FIG. 7 b) for receivingpressurized air. It will be appreciated that by providing airflow, thesurgical site remains dry while the capsulotomy is performed.Pressurized airflow also serves to keep the anterior chamber of the eyeopen and expanded while the lens capsule is being opened.

Referring to FIG. 2, both inner tube 20 and outer tube 18 are coupled toa spring mechanism 54 located in main housing 12, for enabling combinedmovement of inner tube 20 and outer tube 18 out of sleeve 52, as well asfor enabling movement of inner tube 20 within outer tube 18. This willbe described further herein. It will be noted that as shown in FIG. 2,inner tube 20 is positioned inside of outer tube 18.

According to a preferred embodiment, all elements shown in FIG. 2 aredisposable, and are intended for a single use. This includes housing 12,spring mechanism 54, inner tube 20, outer tube 18, sleeve 52, as well asburning element 30 (to be described herein below).

Referring to FIGS. 3 a and 3 b, an extendable-retractable burningelement 30 is connected to the end of inner tube 20. FIG. 3 aillustrates the burning element 30 in its retracted state, within thesleeve 52. FIG. 3 b illustrates the burning element 30 after it has beenextended out of the sleeve 52.

Burning element 30 includes a first band 34 and a second band 36, whichare formed from electrically conductive material such as, though notlimited to, a tungsten alloy. The opposite ends of each band 34, 36 arevertically connected between the end of inner tube 20 and tip 46 ofouter tube 18. Movement of inner tube 20 in the direction of tip 46 ofouter tube 18 causes first band 34 and second band 36 to adopt theextended and open configuration, in which bands 34, 36 substantiallyform a circle with one another, as shown in FIG. 6. A spring mechanism54 is provided for enabling movement of inner tube 20 and of outer tube18. It is appreciated that other mechanisms could be employed, as arewell known in the art, for effecting outward movement of inner tube 20and outer tube 18.

Sleeve 52 covers outer tube 18 and inner tube 20 during passage of thetip of the capsulotomy tool 10 through the corneal incision. Byproviding sleeve 52 as a cover for outer tube 18, as well as for innertube 20 and burning element 30, the entry into the eye can beaccomplished quickly and with minimal friction.

Referring to FIG. 3 b, once the anterior chamber has been reached, outertube 18 and inner tube 20 are advanced from the end of sleeve 52. Whentip 46 is in proximity to the lens capsule, inner tube 20 is advanced soas to cause burning element 30 to be switched from the retractedconfiguration to the extended and opened configuration (see FIGS. 4, 5,and 6). The burning element is then positioned on the capsule. A briefpulse of electricity sent through the tool then causes bands 34, 36 ofburning element to heat up and burn an opening in the lens capsule.

As mentioned previously, sleeve 52 also serves the purpose of providinga seal against the cornea once the end of capsulotomy tool 10 has beeninserted into the eye. It will be noted that in FIG. 1, sleeve 52conceals outer tube 18 and burning element 30 from view.

In the retracted configuration, bands 34, 36 of burning element 30 arepositioned substantially flattened and parallel to one another, directlyabove extension 48 of outer tube 18. In FIGS. 1, 2, 3 a and 3 b, burningelement 30 is in the retracted configuration (in FIG. 1, the burningelement is not visible). In FIGS. 1, 2, and 3 a burning element 30 islocated inside of sleeve 52. In this position, the end of capsulotomytool 10 can be inserted into a relatively small corneal incision, on theorder of 1-2 millimeters.

In FIG. 3 b, burning element 30 has been partially advanced out ofsleeve 52, though it is still in the retracted configuration. Movementof burning element 30 out of sleeve 52 is accomplished by moving outertube 18 and inner tube 20 such that extension 48 and burning element 30become exposed from the end of sleeve 52 Thereafter, inner tube 20 ismoved towards tip 46 of outer tube 18, while outer tube 18 remainsstationary, thereby causing each of bands 34, 36 to assume an arched,semi-circular configuration.

Referring to FIGS. 4-6, the extended and opened configuration is shown,though in FIG. 5, bands 34, 36 have been only partially opened.

The height of bands 34, 36 is about 200 microns higher than that ofinner tube 20 and tip 46, so that when the edges of bands 34, 36 contactthe capsule, no other elements of capsulotomy tool 10 will contact it.Inner tube 20 is provided with a slot 60 formed in the upper edge at theend thereof for accommodating the additional height of bands 34, 36.

Referring to FIGS. 5 and 6, the length of first and second bands 34, 36is designed according to the size of the capsulotomy that is required.For example, for a capsulotomy of 4-5 millimeters, a band length ofabout 7 millimeters is required. The band length is approximately halfthe circumference of the required capsulotomy. Extension 48 of outertube 18 must also be of sufficient length so as to accommodate bands 34,36 when they are in the flattened, retracted configuration. The angle ofbeveled edge 50 can be made larger or smaller depending on the length ofextension 48.

Optionally, before use the burning element 30 is removed from the tool10, so that the size of the burning element can be selected in order tochoose the size of the capsulotomy. Preferably, several removableburning elements can be designed having longer or shorter bands, inorder perform a capsulotomy having a diameter selected from mostpreferred diameters 4, 5, 6 or 7 mm. Removable burning elements of othersizes can also be envisioned.

First and second bands 34, 36 are formed from electrically conductivematerial such as a tungsten alloy or any other suitable element. Innertube 20 and outer tube 18, are both formed, at least partially, fromelectrically-conductive material. Extension 48 and tip 46 of outer tube18, are likewise formed from the same material. Inner tube 20 and outertube 18 define opposite poles of an electrical circuit, and they aredesigned so as to be electrically insulated from one another.

To perform a capsulotomy, a brief low-voltage electrical pulse is passedthrough bands 34, 36. When a current is passed through inner tube 20,bands 34, 36, tip 46, extension 48, and returning through outer tube 18,bands 34, 36 will heat up (or vice versa depending on the polarity).

It will be appreciated that a switch is provided such that theelectrical circuit can be completed only when burning element 30 is inthe extended configuration, so as to prevent premature heating ofburning element 30.

Reference is now made to FIGS. 7 a and 7 b, and to a system for theperformance of a capsulotomy employing the capsulotomy tool describedabove.

Capsulotomy tool 10 is coupled to a handle 72 which facilitatesmaneuvering of tool 10 by the surgeon. Handle 72 houses a motor (notshown) that is connected to spring mechanism (54, see FIG. 2) of mainhousing 12 for enabling reversible movement of the outer tube 18, theinner tube 20, and the extending and retracting of the burning element30.

Handle 72 is coupled to an air pressure unit 74 via an air tube 76having a connector 96 at the end thereof, for supplying pressurized airto the surgical site during performance of the capsulotomy. Air pressureunit 74 preferably includes a control 78 and a display 80 fordetermining the amount of pressurized air delivered to the air channelof capsulotomy tool 10.

Handle 72 is further coupled to a capsulotomy and movement control unit82 via a power cable 84 having a connector 94 at the end thereof, forsupplying electrical current and movement control to capsulotomy tool10. Capsulotomy and movement control unit 82 also includes a control 86as well as a display 88 for determining the amount of electrical currentapplied through power cable 84 to capsulotomy tool 10. Power cable 84 isconnected to the motor inside of the handle 72 for facilitating movementof the outer tube 18 and inner tube 20 of capsulotomy tool 10.

A foot-pedal control switch 90 is also connected to capsulotomy andmovement control unit 82 via a cord 92. Foot-pedal control switch 90enables the surgeon to control the movement of the inner and outer tube20, 18 and the extending and the retracting of the burning element 30,as well as applying of electrical current, with his foot.

Operation of capsulotomy tool 10 will now be described, when used forcreation of a seared capsulotomy opening during cataract surgery.

In FIGS. 8-13, illustrations are schematic and relative sizes are notnecessarily accurate. In reality, the capsulotomy opening encompassesapproximately half to two thirds of the area of the lens, with thecapsulotomy opening usually being within the range of 4-7 mm.

Referring to FIGS. 8 a and 8 b, the surgeon first makes a small incisionin the cornea 100 of the eye 102, preferably on the order of 1-2millimeters diameter, using a standard scalpel 104.

Referring to FIGS. 9 a and 9 b, following formation of an incision inthe cornea 100, the end of capsulotomy tool 10 is inserted through theincision, with capsulotomy tool 10 in the configuration shown in FIG. 1,with inner tube 20, outer tube 18 and burning element 30 disposed insideof sleeve 52. A burst of pressurized air is delivered to the cornea 100,through air channel 24 present at the hollow center of inner tube 20(shown in FIG. 2). The pressurized air assists in retaining the shape ofthe cornea 100, and moves fluids to behind the lens 106, allowingfurther steps of the procedure to be performed on a relatively dry lens106.

Referring to FIG. 10, after the eye is entered, the surgeon usesfoot-pedal control switch 90 to advance outer tube 18, inner tube 20(disposed inside of outer tube 18), and burning element 30, to extendand protrude from the end of sleeve 52 (FIG. 3 b).

Referring to FIG. 11, burning element 30 has been exposed, and innertube 20 is advanced via foot-pedal control switch 90 such that bands 34,36 of burning element 30 are pushed towards tip 46 of outer tube 18while outer tube 18 remains stationary. This causes bands 34, 36 ofburning element 30 to switch from a substantially flattenedconfiguration (shown in FIG. 10), to semi-circular configuration (shownin FIG. 11) wherein bands 34, 36 of burning element 30 substantiallyform a circle with one another (also shown in FIG. 6).

With burning element 30 thus extended and circular, the surgeon lowerstool 10 such that the lens capsule 106 is contacted by bands 34, 36 ofburning element 30.

A low-voltage electrical pulse is then applied using foot-pedal controlswitch 90, and bands 34, 36 heat up such that a capsulotomy opening isburned in the lens capsule 106 where bands 34, 36 are positioned.

Referring to FIG. 12, bands 34, 36 are then returned to the retractedconfiguration via backwards movement of inner tube 20. The capsulotomyopening 108 seared using the invention is apparent in the center of FIG.12. Closing of bands 34, 36 causes any excess capsular and cortical lensmaterial seared from the area of the capsulotomy 108 to be retainedwithin bands 34, 36, allowing removal of this excess material.

Referring to FIG. 13, all internal elements of the tool 10, includingburning ring 30 and inner and outer tubes 20, 18, have been retracted towithin the sleeve 52, in preparation for removal of the tool 10 from theeye 102. Apparent at the center of FIG. 13 is the final capsulotomyopening 108 formed using the capsulotomy tool and system of theinvention. The tool 10 is then removed from the eye 102, and theremainder of the cataract surgery can be performed via the capsulotomyopening 108 seared.

FIGS. 14 and 15 describe a predicament that may occur, in which theelectrical current has surged above the desirable range of voltage, andone or both of the bands have broken in a manner that prevents removalof the tool from the eye. Recall that the tool is inserted through asmall opening of 1-2 millimeters, and then the burning ring is opened toa larger, circular configuration. Should the burning ring then break inthe larger configuration, it is difficult to effect its removal from theeye. The solution to this problem is described in FIGS. 16-18, hereinbelow.

Referring to FIG. 14, the bands of burning element 30 are shown afterrandom breakage has occurred at the center of each band, due to anelectrical surge. This breakage has lead to two pairs of band segments:band segments 35, 37 which remain connected to the end of inner tube 20,and band segments 39, 41 which remain connected to tip 46 of outer tube18. Band segments (35, 39, 37, 41) remain in loose contact with oneanother, giving the appearance in FIG. 14 of being intact. However, thetips of the diamond-shape formed, at the center of the bands, representsevered bands. When attempts are made to retract the broken bands of theburning element, by effecting pulling of inner tube 20 to within outertube 18 and within sleeve 52, band segments 35, 37 may move towards themidline of the tool and can be retracted. However, band segments 39, 41remain open and cannot be retracted, as is more readily apparent in FIG.15.

Referring to FIG. 15, segments 35, 37 have easily been retracted intosleeve 52 in the same manner as bands 34, 36 were designed to retract.However, segments 39, 41, form an arrowhead which extends beyond thesize of the incision in the eye, and cannot be retracted into sleeve 52or be removed from the eye in the extended configuration.

In order to obviate this situation, predefined points of weakness havebeen designed on the bands of the burning element. Referring to FIG. 16,each band 34, 36 of burning element 30 has a groove 45, 43,respectively, close to tip 46. When the electrical current is excessive,breakage will occur at the grooves 45,43, since at these predefinedweakness points the decrease in material mass leads to increasedresistance to the electrical current, resulting in melting of the metalat grooves 45,43.

Referring to FIG. 17, bands 34, 36 of burning element 30 are shown afterbreakage has occurred at the predefined points of weakness (i.e., atgrooves 43, 45 at the distal end of the bands). Thus, in this case, ascan be seen, bands remain connected to inner tube 20 at the proximal endof the burning element. The overturned arrowhead-shape formed by brokenbands 34, 36, allows simple retraction of broken bands back into sleeve52, in preparation for removal of tool 10 from eye 102. Broken bands 34,36 can be moved toward the midline of the tool, parallel to the horizon,and after retraction into the outer tube 18 and the sleeve, broken bands34,36 will not protrude beyond the minimal-sized incision made in theeye.

Referring to FIG. 18, all internal elements of tool 10, including brokenbands 34, 36 have been retracted to within the sleeve 52, in preparationfor removal of tool 10 from eye 102. Tool 10 may now be removed from eye102.

Thus, the improved design shown in FIGS. 16-18, having predefined pointsof weakness, preferably present near the distal tip 46, allows for easyremoval of the tool after undesirable breakage has occurred in the bandsof the burning element.

The system and tool provide an effective and reproducible capsularopening in the lens and allows further steps of cataract surgery, suchas phacoemulsification or an equivalent procedure, and removal ofcataract material.

Thus, the tool of the present invention provides a very significantadvantage when compared with capsulotomy tools of the prior art. Theextendable-retractable burning element allows for performance of acapsulotomy in a quick and efficient manner, leaving a capsular openingthat is clean and tear resistant. Moreover, the extendable-retractableburning element allows for entry into the eye via a corneal incision onthe order of 1-2 millimeters, while allowing for a large capsulotomy,for example, 5-7 millimeters. Using the capsulotomy tool of the presentinvention, the surgical procedure is simplified, since the surgeon doesnot need to use a separate device for providing pressurized air to thesurgical site.

Using the present invention, a complete circle or a complete oval-shapedsearing takes place, so that there is no need for tearing of the lensusing forceps, which would be difficult to perform and to control.

Having described the invention with regard to certain specificembodiments thereof, it is to be understood that the description is notmeant as a limitation, as further modifications will now become apparentto those skilled in the art, and it is intended to cover suchmodifications as fall within the scope of the appended claims.

1. A tool for performing a capsulotomy, comprising; (a) a main housinghaving a proximal end and a distal end; (b) an extendable-retractableburning element coupled to said distal end of said main housing andadapted for being switched between a retracted configuration and anextended configuration; (c) an inner tube extending longitudinallythrough said main housing and extending from the distal end of said mainhousing, wherein said burning element is positioned at the end of saidinner tube; (d) an outer tube that extends longitudinally through saidmain housing and that extends from said distal end of said main housing,wherein said inner tube is disposed inside of said outer tube, andwherein said inner tube is movable with respect to said outer tube forcausing extending and retracting of said burning element; (e) first andsecond electrically-conductive bands comprising said burning element,said bands having opposite ends that are connected between the end ofsaid inner tube and the tip of said outer tube; (f) a groove present oneach of said first and second bands, said grooves providing predefinedpoints of weakness allowing for controlled breakage of said burningelement at said grooves, during an event of excessive electricalcurrent; (g) an airflow channel extending through said main housing andterminating proximal to said burning element; (h) airflow means coupledto the airflow channel for supplying pressurized airflow; and (i)capsulotomy and movement control means coupled to the main housing forproviding electrical current to the burning element and movement controlfor controlling extending and retracting of the burning element, whereinsaid retractable burning element is insertable into the eye through asmall corneal incision when said burning element is in a retractedconfiguration, and said burning element is adapted to perform of acapsulotomy of a predetermined size when it is in an extendedconfiguration and an electrical current is applied to said burningelement.
 2. The tool of claim 1, wherein the outer tube is electricallyinsulated from the inner tube, and wherein each one of said outer tubeand said inner tube defines an opposite pole of an electrical circuit.3. The tool of claim 1, wherein said outer tube comprises acircumferentially truncated extension at the end region thereof, andwherein said outer tube further comprises a tip at which location saidtruncated extension ends.
 4. The tool of claim 3, wherein the outer tubehas a beveled edge located at the interface between said truncatedextension and the remainder of said outer tube.
 5. The tool of claim 1,wherein in said retracted configuration, said bands are positionedsubstantially parallel to one another and above said truncated extensionand wherein in said maximally extended configuration, said bands areconcavely arched so as to form a substantial circle with one another. 6.The tool of claim 5, wherein in the extended configuration, said bandsform a complete circle having a diameter of approximately 4-7millimeters.
 7. The tool of claim 1, wherein said first and second bandsare formed from a tungsten alloy.
 8. The tool of claim 1, whereinmovement of said inner tube towards said tip of said outer tube causessaid burning element to switch from said retracted configuration to saidextended configuration.
 9. The tool of claim 1, further comprising asleeve disposed over said outer tube, said sleeve being formed from anon-conductive material.
 10. The tool of claim 9, wherein said sleeve isformed from plastic or Teflon, having smooth sides such that entry intothe eye can be achieved with minimal friction.
 11. The tool of claim 1,wherein said burning element is removable prior to use, and can beselected from a variety of sized burning elements in order to choose thecapsulotomy size.
 12. The tool of claim 1, wherein said burning elementis capable of searing a capsulotomy having a diameter selected from oneof the following diameters: 4 mm, 5 mm, 6 mm and 7 mm.
 13. The tool ofclaim 1, wherein said airflow channel is located inside of said innertube.
 14. The tool of claim 1, wherein said burning element is capableof searing a complete capsulotomy of a substantially circular or ovalshape, without the need for forceps manipulation or tearing of thecapsulotomy.
 15. The tool of claim 1, wherein said tool is disposable,and is designed for a single use.
 16. The tool of claim 1, wherein eachof said grooves is located adjacent to the distal end of said tool,allowing for retraction of said bands in the event of band breakage. 17.The tool of claim 1, wherein each of said grooves is located adjacent tothe tip of said outer tube.
 18. A system for performing a capsulotomyprocedure, comprising; (a) the capsulotomy tool of claim 1; and (b) acapsulotomy and movement control unit; wherein said tool is inconnection with said capsulotomy and movement control unit for providingelectrical current and movement control to said burning element suchthat when said burning element is extended and heated, an opening isburned on the lens capsule.
 19. The system of claim 18, furthercomprising a handle connecting between said tool and said capsulotomyand movement control unit.
 20. The system of claim 18, furthercomprising an air pressure unit and airflow means coupled to the airpressure unit for directing pressurized air to the surgical site.